Infectious prion proteins, have the ability to reproduce, despite their lack of DNA and RNA. Mammalian cells normally produce prion protein called PrP which during infection with a prion disease, a misfolded protein prion converts the host normal prion protein into its disease shape. Is this event at the critical nano range within the size scale that shape sensing happens to transform good shape into bad shape, is there such a thing as disease shape? Just such a misfolding shape is termed template-directed misfolding. This term refers to the coercion of one protein to change shape and to accumulate in large complexes in a similar way to the prion process. Just such a prion-like template-directed misfolding process has been shown with superoxide dismutase 1, SOD 1 protein. Like bad neighbours attracting more bad neighbours into a neighbourhood, it draws attention to the common nature at this scale perhaps of other misfolded proteins implicated with the spread of pathogenesis of the other neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) also referred to as Lou Gehrig’s disease, Alzheimer’s and Parkinson disease. Dr. Neil Cashman, a Canada Research Chair in Neurodegeneration involving protein folding works on trying to manipulate the particular molecular target to halt the coercion conversion of the SOD1 protein to the disease shape causing form of the misfolded protein at University of British Columbia. According to Cashman, ” Our work has identified a specific target that may stop the progression of ALS with specific treatments.”
Typical examples of prion disease include spongiform encephalopathy, or mad cow disease, Creutzfeldt-Jacob disease, also called Kuru, “Kuru was first noted in the Fore tribe of the Eastern Highlands Province of Papua New Guinea as Australian administrators explored the area in 1953–1959. Kuru (Keru) was reported by W. T. Brown in Kainantu Patrol Report No 8 of 1953/54 (13 January 1954 – 20 February 1954.) .. “The first sign of impending death is a general debility which is followed by general weakness and inability to stand. The victim retires to her house. She is able to take a little nourishment but suffers from violent shivering. The next stage is that the victim lies down in the house and cannot take nourishment and death eventually ensues.” The same reports described the cannibalism practiced by the Fore people. (sourced from Wikipedia)
Microtubule associated protein tau providing active stabilization and flexibility in distal axons as needed. But what is wrong with this diagram? It’s showing tau as a separate, detached entity when in reality it is attached to things. This is the difficulty of deconstruction, the protein is part of an interactive cytoskeleton, tau is NOT in isolation as it functions. Please read on…
Stan Prusiner discovered prions in the early 1980’s. He was initially ridiculed about his so-called heretical findings that prion protein could become prion disease without DNA or RNA replication. A year ago during an evening lecture held at the Woods Hole Marine Laboratory Prusiner gave a passionate lecture, presenting strong evidence that tau, which is a protein that stabilizes microtubules, can accumulate in the brain cells, termed tauopathies, are essentially prion diseases.
Prusiner made a specific reference to comparing punch drunk boxers with frontotemporal neurodegenerative disease to what is frequently associated with minor head injuries caused by improvised explosive devices (IED) blasts in Iraq and Afganistan. According to Prusiner, frontotemporal dementia is a common condition after blast injury concussions suffered by soldiers is a prion disease. Prusiner showed graph after graph as well as clinical cases of people who developed frontotemporal dementia after repeated mild head injuries, leading to symptoms similar to post-traumatic stress syndrome, drug abuse and addiction, emotional lability, depression with progressive loss of intellectual capacity and motor function. Stan Prusiner received the Nobel Prize in Physiology or Medicine in 1997 for his seminal work on discovering prion disease.
Extensive studies on misfolded protein have revealed that the rate of protein folding is determined by the viscosity of the artificial medium is located plus is strongly influenced by pH and temperature of the ambient conditions. But still protein folding is not fully understood despite the progress. Normal folding sequences are guided by chaperones guiding the dance of the process and improperly folded proteins are usually promptly destroyed by proteolytic enzymes, why this does not happen with prion like misfolding is according to Chris Dobson head of a prion research group at Cambridge University, UK, is ‘one of the grand challenges of modern science.’
So the question now becomes sort of obvious if the reader has been following from previous posted essays, does tau interact with a tensegrity structure inside the brain? Is tau playing its role within a tensegrity structure? This is the research question I have been pursuing now for a long time. My scientific gut was telling me yes but I didn’t have the evidence to examine. Now I do and here it is. The article I am citing sounds like a mouthful and it involves some snappy experimental design but I will attempt to guide you through this tunnel if you are unfamiliar here take my hand and listen as we plunge into the darkness, gulp ! First some post-transcriptional biology 101.
So what is the point of the diagram above ? Let’s go at it carefully step by step this kind of thing goes on in your gut your brain whatever, pay attention I’m talking about how you work at a scale you’re not used to, that’s all.
Post-transcriptional regulation is the control of gene expression at the RNA level, therefore between the transcription and the translation of the gene.
The first instance of regulation is at transcription (transcriptional regulation) where due to the chromatin arrangement and due to the activity of transcription factors, genes are differentially transcribed.
After being produced, the stability and distribution of the different transcripts is regulated (post-transcriptional regulation) by means of RNA binding protein(RBP) that control the various steps and rates of the transcripts: events such as alternate splicing, nuclear degradation (exosome), processing, nuclear transport(three alternative pathways), sequestration in DCP2-bodies for storage or degradation, and ultimately translation
These proteins achieve these events thanks to a RNA recognition motif (RRM) that binds a specific sequence or secondary structure of the transcripts, typically at the 5′ and 3′ UTR of the transcript.
Modulating the capping, splicing, addition of a Poly(A) tail, the sequence-specific nuclear export rates and in several contexts sequestration of the RNA transcript occurs in eukaryotes. (Thank you Wikipedia)
hnRNP K post-transcriptionally co-regulates multiple cytoskeletal genes need for axonogensis Development 138, pages 3079-3090 (2011) authors: Yuanyuan Liu and Ben G. Szaro Department of Biological Sciences and the Center for Neuroscience Research, University of Albany, NY, 12222, USA
“Control of expression of proteins associated with the cytoskeleton is crucial for meeting changing demands for structural materials as axonal growth shifts between bouts of extension, pausing, retraction and branching. Not only must their total amount of protein available be appropriate to sustain growth, but also the relative abundance among constituents of the three [polymers must be kept in balance. Imbalances for example among type IV neurofilament (NF) subunits leads to pathogenic aggregates. Overexpression of the microtubules associated tau protein relative to the neurofilaments induces premature retraction of developing neurites. ” The researchers chose to use Xenopus a genus of frog native to Sub-Saharan Africa for the neurofilament study since other investigators have used the developing mammalian neurons from the optic axons demonstrating that just such a control to involve an interplay between modulations in gene transcription and post-transcriptional control of nuclear export, turnover and translation of the RNAs.” The authors queried whether such interplay extended to other cytoskeletal constituents for the basis of their experiments. The focused on one such entity, ribonucleoproteins, (RNP) that are known to bind neurofilament messenger RNA have a major role in directing such coordinated expression, in particular hnRNP binds all three neurofilament triplet RNAs.The researhers sought to investigate the function of previous cell line work having established a shuttling behavior between the nucleus and the cytoplasm, participating in the multiple aspects of RNA metabolism. The protein is a member of the triple K-homology RNA-binding domain RNP, which is currently modeled to be understood as a scaffolding protein, in the words of the investigators, “… controlling its target RNAs through combinatorial interactions with multiple partner, which can bind hnRNP K directly, depending on its phosphorylation state or interact indirectly through steric hinderance and competition whilst binding.”
“In developing Xenopus neurons, hnRNP K plays an essential role in regulating the nuclear export and translation of the middle neurofilament triplet subunit’s mRNA. In these neurons, hnRNP K knockdown also leads specifically to a cell-autonomous failure of the axons to develop, without significantly affecting either neural pattern formation or terminal neuronal specification. Because loss of middle neurofilament by itself is insufficient to account for a complete failure of axons to develop, hnRNP K must post-translationally regulate additional transcripts used to make the axon.
The authors test this hypothesis by demonstrating that hnRNP K plays its critical role in axon outgrowth, downstream of neuronal specification in the initial establishment of cell polarity, by functioning as an RNA-binding protein that co-regulates the expression of multiple transcripts. These transcripts include components associated with microtubules, microfilaments and neurofilaments that collectively organize these polymers into an axon. Usually studied individually, these same polymers participate into a tensegrity structure. Now things get very interesting because we’re finally talking about interactions involving proteins within a tensegrity structure, which gets to the primary signalling shape that controls an axon among many axons like a few billion neurons with axons in our brain. If the basic units describe a tensegrity network the whole thing, the entire brain is one massive tensegrity network structure.
The authors have employed the KNOCKDOWN technique which will be briefly described:
‘Gene knockdown refers to techniques by which the expression of one or more of an organism’s genes is reduced, either through genetic modification(a change in the DNA of one of the organism’s chromosomes ) or by treatment with a reagent such as a short DNA or RNA olginucleotide with a sequence complementary to either a mRNA transcript or a gene. If genetic modification of DNA is done, the result is a “knockdown organism”. If the change in gene expression is caused by an oligonucleotide binding to a mRNA or temporarily binding to a gene, this results in a temporary change in gene expression without modification of the chromosomal DNA and is referred to as a “transient knockdown”.
In a transient knockdown, the binding of this oligonucleotide to the active gene or its transcripts causes decreased expression through blocking of transcription(in the case of gene-binding), degradation of the mRNA transcript (e.g. by small interfering RNA (siRNA) orRNas-H dependent antisense) or blocking either mRNA translation, pre-mRNA splicing sites or nuclease cleavage sites used for maturation of other functional RNAs such as miRNA(e.g. by -morpholingo oligos or other RNase-H independent antisense.) The most direct use of transient knockdown is for learning about a gene that has been sequenced,but has an unknown or incompletely known function, an experimental approach known as reverse genetics. Researchers draw inferences from how the knockdown differs from individuals in which the gene of interest is operational. Transient knockdowns are often used in developmental biology because oligos can be injected into single-celled zygotes and will be present in the daughter cells of the injected cell thru embryonic development’ sourced from Wikipedia
When the term oligos is employed the term comes from the Greek prefix, meaning having few, having little, which is a short nucleic acid polymer, typically with fifty or fewer bases. These oligos can be formed by bond cleavage from longer segments but they are more readily assembled, synthesized using automated synthesizers to as much as 200 bases. Oligonucleotides bind to their respective complimentary oligonucleotides in this case RNA to form duplexes. This basic property of oligonucleotides is employed as probes for detecting RNA or DNA such as used in DNA microarray, Southern blots and synthesis of artificial genes, especially antisense oligonucleotides. Antisense nucleotides. are single strands of RNA in this experiment, they can also be single strands of DNA. With antisense RNA they prevent protein translation of certain messenger RNA strands by binding to them. If binding takes place this RNA hybrid can be degraded by the enzyme RNaseH.
Let’s take a breather here, if the reader is not totally familiar with these procedures and concepts this whole essay is quite a chunk of material to absorb let alone comprehend. However I will get to the conclusions from this excellent paper. For me it is the confirmation of an odyssey that I started a long time ago with that walk on the beach in one of my first essays, almost a year ago writing and almost two decades ago as the original thoughts exploded into my mind’s eye during Montreal’s Great Ice Storm winter of 1998. The spark back then was Donald Ingber’s majestic essay in Scientific American entitled the architecture of life in cells, how at the basic foundation, tensegrity, cells balanced in associated attachments with compression and tension, these attachments are at the fundamental level of shape that determines both the normal and abnormal output of cell ensembles at a local level into networks all attached together scaling up to the size of the human brain.
I had actually contacted Dr Ingber emailing at Harvard asking him, “Is our brain a tensegrity structure?” and his answer to me was essentially, ‘that is what it appears to be.’ And now with this paper I have been carefully attempting to summarize the essence of prions being associated with the long-term effects off multiple concussions, the very basic aspect becomes prions acting within a cytoskeletal environment that leads to a concussive dementia as evidenced by this collection of damaged brain that fits the dementia pugilistic profile. The background of the tau interaction inside the architecture is within a tensegrity designed system which is inside our brains.
Here are the authors final conclusions.
“More importantly, this study provides the first direct experimental evidence that hnRNP K is the nexus of a novel, post-translational regulatory module that coordinates the synthesis of structural proteins used to organize microtubules, microfilaments and NFs into an axon. Although traditionally studied individually, these polymers in fact participate in a tensegrity structure (Ingber, 2003), forming a network for which structuromechanical properties depend on interactions among the various polymer types, which are mediated by proteins that associate with each polymer. For example, Type IV neuronal intermediate filaments (e.g. NF-L, NFM and -internexin-like subunits) possess extensive carboxyterminal domains that radiate outward from the filament and interact with both adjacent NFs and microtubules to preserve their alignment (Geisler et al., 1983; Hirokawa et al., 1984; Miyasaka et al., 1993). Similarly, tau not only aligns axonal microtubules but also mediates microtubule-microfilament interactions (Farias et al., 2002; Hirokawa et al., 1988; Weingarten et al., 1975), and Arp2, as part of the Arp2/3 complex, both forms branch points of the microfilament network and bridges them to microtubules through WHAMM [WAS protein homolog associated with actin, Golgi membranes and microtubules (Campellone et al., 2008; Disanza and Scita, 2008)].”
The results of the single and triple-knockdown experiments for XNIF, Arp2 and tau demonstrated this tensegrity principal at work. The defects seen with individually disrupting expression of each cytoskeletal-associated protein were consistent with their known roles in consolidating axon outgrowth, organizing microtubules into parallel arrays, and filopodia-formation and filament branching, respectively, none of which compromised the overall length and patterning of axon outgrowth severely. By contrast, triple knockdown of these proteins led synergistically to severe defects in axon outgrowth accompanied by an uncoupling of the cytoskeletal polymers, which were, nonetheless, synthesized. Although a nice demonstration of tensegrity at work, more fundamental is the novel finding that the expressions of proteins fulfilling this tensegrity function are post-transcriptionally coregulated through a shared RNA-binding protein.” The opening question concerned probing the supposed relationship of prion disease progression which appears with deformed protein folding, effectively uncoupling the cytoskeletal polymers shape structure in the neighborhood vicinity, is this a biological overlap as if multiple concussions mimics the disease effects of the prions? Are multiple concussions to be considered as a disease progression?